/Engine/Plugins/Animation/LiveLink/Source/LiveLink/Public/LiveLinkBlueprintLibrary.h
Set the subject's from a specific source to enabled, disabling the other in the process. Only 1 subject with the same name can be enabled. At the start of the frame, a snapshot of the enabled subjects will be made. That snapshot dictate which subject will be used for the duration of that frame. SetSubjectEnabled will take effect on the next frame.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="LiveLink") static void SetLiveLinkSubjectEnabled ( const [FLiveLinkSubjectKey](API\Runtime\LiveLinkInterface\FLiveLinkSubjectKey) SubjectKey, bool bEnabled )